Elderly taxpayer never filed 2012 return (illness, family issues). In late 2016 she was contacted by state (never heard from IRS) so, with considerable difficulty, we got together information and filed both state and federal returns in early 2017. She ended up with balances due which she paid. Unfortunately I made a mistake on Federal 1040 and calculated balance due using withholding am't of $500 (which was state w/h) instead of correct am't of $800. So she overpaid about $300. Original return was filed in January 2017 and an amended return filed in March 2017 requesting a refund. I have received first time abatement for failure to file and failure to pay so there is only interest involved as an additional charge to her. One person I spoke to at the IRS says they won't refund the $300 (minus interest) as over 3 years have passed since filing deadline.

Is there any way she can get back her $300? The person I spoke to at the Practitioner Priority line was vague and mentioned that there might be an exception if she filed the original return in 2017...which she did...and she might have 2 more years to request refund. Does anyone have any information about such an exception? I feel really bad as it was my error, doing an old return by hand.